1. Field of the Invention
The present invention relates generally to devices for securing electrical plugs to connectors with which the plugs are mated and, more particularly, but not by way of limitation to devices for securing ribbon cable plugs to printed circuit board connectors.
2. Brief Description of the Prior Art
Computer systems are put together using a variety of peripherals which are selectable by the user to tailor the system to his personal needs. Once the peripherals have been selected and, if required, mounted in the computer case, they are electrically integrated into the system via a system bus which provides communications between various parts of the system including a microprocessor which controls the operation of the system as a whole. For example, disc drives are commonly integrated into a computer system via a controller card that mounts in an expansion slot that provides connections to the system bus. The disc drive proper is then connected to the controller card via a ribbon cable upon which is mounted a multi-pin plug that is mated with a connector on a printed circuit board mounted on the disc drive case.
While the use of a ribbon cable to make electrical connections to a disc drive or other peripheral device in this manner is generally problem free under normal operating conditions, it has been found that problems can arise in abnormal circumstances. In particular, repeated mechanical shocks delivered to a computer, for example, during transport, can result in a ribbon cable plug "walking" off a printed circuit board connector; that is, the plug is jarred loose from the connector in a series of small steps. The general result is that the computer will no longer be operable for its intended purpose. Again, for example, if the plug mates with a connector on a disc drive, programs and data will not be available when an attempt is subsequently made to place the computer in service.
While, conceptually, the problem of unmating might be solved by increasing the force necessary to unmate the ribbon cable plug and printed circuit board connector, such an increase would present new problems. The mating is commonly effected by forcing pins on the plug into sockets formed in the connector so that frictional forces hold the plug and connector together once the two have been mated. While these frictional forces can be made as large as one wishes, the result of doing so may very will be damage to the pins and sockets. As will be clear to those of skill in the art, a large number of connections will generally be made to the system bus in a limited space with the result that the pins and sockets tend to have limited mechanical strength. Consequently, both the mounting of the plug and, should it be necessary for testing for example, the removal of the plug can give rise to damage to the pins and the sockets if the mating forces between them are large. Thus, increasing the mating force is not an attractive solution to the problem. Moreover, the connector may be mounted on the printed circuit board by solder joints between contacts in the board and in the connector and these joints can be damaged by large forces exerted on the contacts in mating the plug and the connector.
Another possibility for solving the problem would be the use of some type of clip that would fit over the ribbon cable plug and attach to the printed circuit board connector. A problem with this approach is the length that would be required for the clip and a need to secure the clip to the connector at the ends of the clip. Since the ribbon cable extends from one side of the plug, a securing clip would have to extend along the long axis of the plug, at least the width of the ribbon cable, to clear the ribbon cable and the cable would interfere with connections between the clip and connector that might be made along the length of the clip.
The problem is exacerbated where the printed circuit board connector is a so-called 3-in-1 connector which is commonly used to make electrical connections to a disc drive. This type of connector is comprised of a signals section, which mates with the ribbon cable plug leading to the system bus, an address section by means of which the disc drive can be addressed for use, and a power section by means of which power is supplied to the disc drive from the computer power supply. These sections are placed side-by side so that the connector can be mounted along an edge of the printed circuit board which supports circuitry used in the operation of the disc drive. As a result, a suitable clip for securing the ribbon cable connector to the printed circuit board connector would have to have a width substantially equal to the width of the printed circuit board and would have to be secured to the connector at its ends. While such a securing device might be constructed, doing so would generally require the use of metal parts which not only could give rise to short circuits but, since the device would be secured to the connector at widely spaced points, would entail shaping operations that could give rise to undesirable manufacturing expenses. Consequently, prior to the present invention, no really suitable means has been developed to secure ribbon cable plugs to printed circuit board connectors.